SERVER-53035 ThreadAssertionMonitor

3 files changed, 240 insertions, 0 deletions

diff --git a/src/mongo/unittest/SConscript b/src/mongo/unittest/SConscript
index 7b7e09341dd..680eb3ae258 100644
--- a/src/mongo/unittest/SConscript
+++ b/src/mongo/unittest/SConscript
@@ -99,6 +99,7 @@ env.CppUnitTest(
         'unittest_test.cpp',
         'fixture_test.cpp',
         'temp_dir_test.cpp',
+        'thread_assertion_monitor_test.cpp',
     ],
 )
 
diff --git a/src/mongo/unittest/thread_assertion_monitor.h b/src/mongo/unittest/thread_assertion_monitor.h
new file mode 100644
index 00000000000..157eb3c4885
--- /dev/null
+++ b/src/mongo/unittest/thread_assertion_monitor.h
@@ -0,0 +1,140 @@
+/**
+ *    Copyright (C) 2020-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <exception>
+
+#include "mongo/stdx/condition_variable.h"
+#include "mongo/stdx/mutex.h"
+#include "mongo/stdx/thread.h"
+#include "mongo/unittest/unittest.h"
+#include "mongo/util/scopeguard.h"
+
+namespace mongo::unittest {
+
+/**
+ * Worker threads cannot use ASSERT exceptions, because they'll normally crash the
+ * process. We provide a way for a worker to transfer ASSERT failures to the
+ * main thread to be rethrown from there.
+ *
+ * The main thread has to be structured such that it's waiting
+ * on this monitor while all other work happens in workers.
+ */
+class ThreadAssertionMonitor {
+
+public:
+    // Monitor will `wait()` on destruction, blocking until a `notifyDone()` call has occurred.
+    ~ThreadAssertionMonitor() noexcept(false) {
+        wait();
+    }
+
+    /** Spawn and return a `stdx::thread` that invokes `f` as if by `exec(f)`. */
+    template <typename F>
+    stdx::thread spawn(F&& f) {
+        return stdx::thread{[this, f = std::move(f)]() mutable { exec(std::move(f)); }};
+    }
+
+    /** Spawn a thread that will invoke monitor.notifyDone()` when it finishes. */
+    template <typename F>
+    stdx::thread spawnController(F&& f) {
+        return spawn([this, f = std::move(f)]() mutable {
+            auto notifyDoneGuard = makeGuard([this] { notifyDone(); });
+            exec(std::move(f));
+        });
+    }
+
+    /** Invokes `f` inside a try/catch that routes any ASSERT failures to the monitor. */
+    template <typename F>
+    void exec(F&& f) {
+        try {
+            std::invoke(std::forward<F>(f));
+        } catch (const unittest::TestAssertionFailureException&) {
+            // Transport ASSERT failures to the monitor.
+            bool notify = false;
+            {
+                stdx::unique_lock lk(_mu);  // NOLINT
+                if (!_ex) {
+                    _ex = std::current_exception();
+                    notify = true;
+                }
+            }
+            if (notify)
+                _cv.notify_one();
+        }
+    }
+
+    void notifyDone() {
+        {
+            stdx::unique_lock lk(_mu);
+            _done = true;
+        }
+        _cv.notify_one();
+    }
+
+    // Blocks until `notifyDone` is called.
+    // Throws if an ASSERT exception was reported by any exec invocation.
+    void wait() {
+        stdx::unique_lock lk(_mu);
+        do {
+            _cv.wait(lk, [&] { return _done || _ex; });
+            if (_ex)
+                std::rethrow_exception(std::exchange(_ex, nullptr));
+        } while (!_done);
+    }
+
+private:
+    stdx::mutex _mu;  // NOLINT
+    stdx::condition_variable _cv;
+    std::exception_ptr _ex;
+    bool _done = false;
+};
+
+/**
+ * Covers probably most cases of multithreaded tests.
+ * The body of a test can be passed in as an `f` that
+ * accepts a `unittest::ThreadAssertionMonitor&`.
+ * `f(monitor)` will to become the body of a "controller" thread.
+ *
+ * Any `stdx::thread(...)` constructors in the test must then be
+ * converted to `monitor.spawn(...)` calls. Then the ASSERT
+ * calls in the test will be managed by the monitor and propagate
+ * to be rethrown from the main thread, cleanly failing the unit test.
+ *
+ * The controller thread is joined inside this function,
+ * but user code is still responsible for joining the spawned
+ * worker threads as usual.
+ */
+template <typename F>
+void threadAssertionMonitoredTest(F&& f) {
+    ThreadAssertionMonitor monitor;
+    monitor.spawnController([&, f] { std::invoke(f, monitor); }).join();
+}
+
+}  // namespace mongo::unittest
diff --git a/src/mongo/unittest/thread_assertion_monitor_test.cpp b/src/mongo/unittest/thread_assertion_monitor_test.cpp
new file mode 100644
index 00000000000..f20257e2030
--- /dev/null
+++ b/src/mongo/unittest/thread_assertion_monitor_test.cpp
@@ -0,0 +1,99 @@
+/**
+ *    Copyright (C) 2020-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kTest
+
+#include "mongo/unittest/thread_assertion_monitor.h"
+
+#include "mongo/logv2/log.h"
+#include "mongo/unittest/unittest.h"
+
+namespace mongo::unittest {
+namespace {
+
+TEST(ThreadAssertionMonitor, Trivial) {
+    ThreadAssertionMonitor monitor;
+    monitor.notifyDone();  // Somebody always has to call notifyDone or dtor will wait forever.
+}
+
+TEST(ThreadAssertionMonitor, ControllerInStdxThread) {
+    ThreadAssertionMonitor monitor;
+    stdx::thread{[&] { monitor.notifyDone(); }}.join();
+}
+
+TEST(ThreadAssertionMonitor, OnlyControllerInSpawn) {
+    ThreadAssertionMonitor monitor;
+    monitor.spawn([&] { monitor.notifyDone(); }).join();
+}
+
+TEST(ThreadAssertionMonitor, OnlyControllerInSpawnController) {
+    ThreadAssertionMonitor monitor;
+    monitor.spawnController([] {}).join();
+}
+
+TEST(ThreadAssertionMonitor, WorkerExecOk) {
+    ThreadAssertionMonitor monitor;
+    monitor.spawnController([&] { monitor.spawn([&] { ASSERT_EQ(1, 1) << "Worker ok"; }).join(); })
+        .join();
+}
+
+TEST(ThreadAssertionMonitor, WorkerExecFail) {
+    ThreadAssertionMonitor monitor;
+    monitor.spawnController([&] { monitor.spawn([&] { ASSERT_EQ(1, 2) << "Oops"; }).join(); })
+        .join();
+    try {
+        monitor.wait();
+        FAIL("Expected monitor.wait() to throw");
+    } catch (const TestAssertionFailureException& ex) {
+        ASSERT_STRING_SEARCH_REGEX(ex.what(), "Oops");
+    }
+    LOGV2_INFO(5182100, "monitor.wait finished");
+}
+
+TEST(ThreadAssertionMonitor, ThreadAssertionMonitoredTestTrivial) {
+    threadAssertionMonitoredTest([](auto&) {});
+}
+
+TEST(ThreadAssertionMonitor, ThreadAssertionMonitoredTestPassing) {
+    threadAssertionMonitoredTest([](auto& monitor) { monitor.spawn([&] {}).join(); });
+}
+
+TEST(ThreadAssertionMonitor, ThreadAssertionMonitoredTestFailing) {
+    try {
+        threadAssertionMonitoredTest(
+            [](auto& monitor) { monitor.spawn([&] { ASSERT_EQ(1, 2) << "Oops"; }).join(); });
+        FAIL("Expected threadAssertionMonitoredTest to throw");
+    } catch (const TestAssertionFailureException& ex) {
+        ASSERT_STRING_SEARCH_REGEX(ex.what(), "Oops");
+    }
+}
+
+
+}  // namespace
+}  // namespace mongo::unittest